Expansion joint



Sept. 25, 1962 w. R. RINKER ET AL EXPANSION JOINT Filed May 15, 1957 UPPER COMPRESSIVE INVENTORS WILLIAM RRINKER BY ROBERT G. MCGILVREY the United States Patent Office 3, 219 Patented Sept. 25, 1962 Yuri:

Filed May 15, 1957, Ser. No. 659,354 8 Claims. (Cl. 94--18) This invention relates to expansion joints useful to compensate for expansion and contraction in buildings, bridges, paving and various masonry or machine structures. The joints of this invention are especially useful in the construction of concrete roads to compensate for thermal expansion or contraction of roadway slabs.

One of the characteristic features of the joints of this invention is that they are capable of undergoing unusually large dimensional changes, and are therefore well adapted for service in expansion gaps where the amplitude of the expansion and contraction is very large. In road construction, the joints of this invention are advantageously adapted to compensate for thermal expansion and contraction of large amplitude and at the same time provide for sustaining heavy traific loads, for sealing the expansion gap at the junction of adjoining slab, and for maintaining a smooth riding surface across the expansion gap throughout the range of expansion and contraction.

In view of these characteristics, it is feasible to build roads embodying these improved expansion joints so that the roads have considerably fewer but wider expansion gaps than has been the practice heretofore. F or example, by using expansion joints of the type provided by this invention, slabs of concrete for a roadway may be poured in continuous lengths of several hundred feet or more and with expansion gaps of as much as six to twelve inches or more; whereas, prior to this invention in view of the character of the expansion joints proposed by the prior art, roadway slabs have been ordinarily limited in length to appreciably less than one hundred feet and with expan sion gaps in the order of about one inch in width. One wide expansion joint as provided by this invention is much more economical to install and maintain than several smaller joints to compensate for the same amplitude of expansion and contraction. Moreover, the use of widely spaced expansion joints in a roadway substantially reduces the frequency of the objectionable road noise commonly known as expansion joint slap which is audible to the driver of a vehicle as the vehicle traverses many closely spaced conventional joints at high speeds. In fact, with the joints of this invention there is practically no such slap because these joints are designed so that their exposed road surface remains substantially flush with the adjoining concrete roadway surfaces throughout the range of width variation the joints are capable of undergoing. Thus under any temperature conditions the exposed surfaces of these new joints are substantially as smooth as the concrete roadway surfaces.

The general structural features of the joint of this invention include a body of resilient flexible rubber composition adapted for bridging and covering an expansion gap between adjoining structural parts such as concrete road slabs. The rubber body is supported at the mouth of the expansion gap by a series of laterally spaced parallel rigid support members, preferably flat metal plates, extending lengthwise of the gap. Between adjoining supporting members the rubber body is for-med with longitudinal pleat portions. The rigid supporting members are adapted for relative lateral translational displacement in the gap, and the pleat portions are adapted for distortion or bulging into the regions between the supporting members in response to changes in the width of the gap. The supporting members are maintained in spaced parallel relation in the gap by a series of rubber spacers which are laterally compressed between the plates when the gap is reduced in width by expansion of the adjacent parts. In the preferred construction, the spacers are designed so that as they are compressed they are adapted to urge their respective rigid members downward from the body to oppose the elevating or jacking effect on the plate portions which occurs as the pleat portions are progressively distorted between these members.

Details of an expansion joint designed especially for use in a concrete road is shown in the accompanying rawing to illustrate one practical form in which the principles of this invention may be embodied.

in the drawings:

FIG. 1 is a plan view showing a joint of this invention between a pair of concrete road slabs;

FIG. 2 is a sectional elevational view taken along the line 22 of FIG. 1 and showing the joint in an expanded condition;

FIG. 3 is a fragmentary sectional view similar to FIG. 2 but showing the joint in a contracted condition;

FIG. 4 is a fragmentary detail view taken on the line 4-4 of FIG. 2; and

FIG. 5 is a diagram showing certain theoretical considerations involved in the construction.

Referring to FIG. 1, an expansion joint 10 in accordance with this invention is installed in an expansion gap of substantial width between two concrete road slabs 11 and 1'2 having opposing vertical end faces 13 and 14, respec tively, defining the lateral sides of the expansion gap (see also FIG. 2 for numerals 13 and 14). The expansion joint 11? extends across the width of the gap between faces 13 and 14 and for the full length and depth of the gap, transverse to the roadway surfaces 15 of the slabs. These surfaces 15 may extend for hundreds of feet in the direction of the arrows in FIG. 1. As shown in FIG. 2, the opposing ends of slabs 11 and 12 are jointly supported on the subgrade by an underlying sleeper slab 17 having an upper smooth plane surface 18 defining the bottom of the expansion gap. The ends of slabs 11 and 12 are adapted for movement relative to the sleeper slab to vary the width of the gap as a result of thermal expansion and contraction of the slabs.

In its structural detail, the expansion joint 10 includes a body 2% of flexible resilient rubber-like material which covers the open mouth of the expansion gap. The body 2% includes longitudinal margins 23 and 24 engaging end faces 13 and 14, respectively, of the gap and has an upper road surface 25 flush with the roadway surface 15 of the slabs. The upper surface 25 is striated with a series of grooves 26 which are narrow and shallow and which extend lengthwise along the outer surface '25 in laterally spaced parallel relation. The portions of the outer sur face between grooves 26 are plane. Each groove 26 has opposing convexly rounded side surfaces 2 8 which blend smoothly into the plane outer surface portions between the grooves and which converge to a narrow bottom surface 27.

The side of the body directed into the gap, i.e. its inside surface 30, is formed with a series of lengthwise ridges 32, the crests 33 of which are disposed opposite corresponding grooves 26 of the outer surface. In the valleys 34- medially between the crests 33 there is attached to the rubber body 20 the upper edges of a series of fiat vertical rigid metal plates 35 which support the rubber body in the gap. The plates 35 extend longitudinally of the body 20 between successive crests 33 and are arranged so that each plate has its upper longitudinal edge 36 seated in its respective valley 34 and its lower longitudinal edge 37 resting slidably on the surface 18 of the sleeper slab. Each plate is preferably rubber-covered as shown to protect it from corrosion and the upper longitudinal edge 36 of each plate is fastened integrally to the rubber body, for example, by vulcanization when the rubber body is cured.

Near their lower edges 37, the supporting plates 35 are laterally separated one from another in parallel relation by a series of resilient rubber spacers 40 which extend lengthwise between the plates. The upper surfaces of the spacers 40 are crowned or curved convexly as indicated by numeral 41 and on the bottom of each spacer there are ribs or legs 42 on which the spacer is supported on the surface 18 of the sleeper slab. The spacers 4% are preferably resilient rubber and it is convenient to extrude these spacers and vulcanize them prior to their assembly between the plates 35. Preferably the spacers are cemented between the plates after vulcanization or final molding of the body 20 with the plates properly positioned thereon. As hereinafter explained more fully, the spacers are adapted for lateral compression in the manner shown in FIG. 3, thereby effecting lateral translational displacement of the plates 35 in parallelism along the surface 18 when the expansion joint is laterally squeezed, as when the slabs l1 and 12 expand to reduce the width of the gap.

The end-most plates 35a and 35b which respectively support the margins 23 and 24 of the rubber body 20 fit flat against the end faces 13 and 14 of the slabs and, inasmuch as the expansion joint is laterally compressed when installed as is subsequently explained, the end plates 35a and 3512 are in pressure engagement with the end faces of the slabs. To prevent leakage of moisture between these endmost plates and the slabs, preferably the end plates 35a and 3512 are cemented tightly to the end faces 13 and 14 when the expansion joint is installed. The end plates 35a and 35b are additionally secured firmly to the end faces 13 and 14 by means of a series of anchor lugs 45 (see also FIG. 1) attached to the end plates 35a and 35b at spaced intervals lengthwise of the strip. The anchor lugs 45 are connected to the slabs by vertical dowel pins 46 as shown in FIG. 2. The lugs 45 are rigid metal tubes of generally D-shaped cross section which are fastened with their fiat sides 48 abutting their respective end plates by screws 49. The tubes are rubber covered and are open at their upper ends to receive the dowels 46. Each lug 45 fits into a corresponding D-shaped socket 50 molded in the adjoining concrete slab with the bottom piece 51 of the lug resting on the bottom'of its socket 50 so that a hole 52 in the bottom piece 51 registers with a hole 53 in the bottom of the socket. The dowel 46 is then driven through the bottom piece and into hole 53 until an annular shoulder 54 on the dowel is seated on bottom piece 51. The open mouth of the socket 50 is then covered by a thick rubber plug 55 having an upper surface flush with the roadway surface of the slabs.

The expansion joints 10 are normally installed in a highway after the slabs including slab 17 are set up firmly. The width of the expansion gap is controlled when the slabs are poured so that the gap will have an appropriate width for the existing temperature conditions. As noted in the preceding discussion, the expansion gap for this joint is normally very much wider than the conventional narrow expansion gaps which have been previously used in this art. With this joint, the width of the expansion gap may range normally from about six to about tweleve inches, and the amplitude of the thermal expansion and contraction of the ocncrete slabs may be as much as three to four inches or more.

The expansion joint 10 may be made in many different sizes depending on the amplitude of the expansion and contraction of the expansion gap, and the joint may include any number of plates 35 as may be desirable to provide the necessary vertical support for the body portion 20. For modern highways, it may be assumed for design purposes that the road surface 25 of the rubber body is subjected by traflic to vertical pressure force of about pounds per square inch which force must be transmitted through plates 35 to the sleeper slab. With considerations such as these in mind, the optimum number of plates 35 and the size of the joint can easily be determined by those familiar with the road-building art.

At installation, the joint is laterally compressed as it is inserted into the expansion gap, and preferably the joint is designed so that its rubber parts are maintained under lateral or static compression even at the widest position of the gap. Ordinarily the static compression for the widest gap size will be in the order of about 10% of the width of the joint when its rubber parts are uncompressed. This amount of compression is generally desirable to compensate for permanent set of the rubber parts. Preferably the rubber parts will be suitably compounded and treated by techniques familiar to those skilled in the rubber compounding art to minimize permanent compressive set.

When the road slabs 13 and 14 expand longitudinally to reduce the width of the gap, the opposing side plates 35a and 3512 are subjected to intensive opposing compressive forces which tend to laterally deform the expansion joint. FIG. 3 shows the approximate condition of the several parts of the joint when the joint is laterally compressed to about its minimum width. As the joint is laterally compressed, the rubber ridges 32 projecting between the plates are distorted and caused to bulge downwardly between their respective pairs of plates 35. At the same time the grooves 26 tend to close or become progressively narrower so that the upper surface 25 of the rubber body 20 approaches the condition of a plane. The body 20 is designed so that there is practically no distortion or bulging of the portion of the rubber body 20 in the region immediately above the upper edges 36 of plates 35 throughout the range of compression to which the expansion joint is subjected.

As the body 20 is laterally compressed, the spacers 40 are also subjected to lateral compression and thereby displace the plates 35 sideways in parallelism along surface 18 toward the center of the gap. Because of the convexly crowned shape of the upper surfaces of the spacers 40, they are adapted to bulge upwardly toward the body 20. As a result of the upward distortion of the spacers 40 in this manner, a corresponding downward vertical force is transferred to the plates 35 adjoining the spacers tending to maintain the lower edges 37 of the plates seated firmly on the sleeper slab surface 18. Thus, by this arrangement of these spacers 40 the medial portions of the joint are prevented from being displaced upward from the gap, and arching of the body 26 or fanning out of the plates 35 between the side faces 13 and 14 as a result of such compression is avoided.

The diagram of FIG. 5 illustrates certain theoretical considerations useful in designing these joints. This dia gram shows any two intermediate plates 35 and the rubber portions of the joint located between these plates. It will be noted that the depth of each groove 26 in the rubber body 20 terminates above the elevation of the upper edges 36 of plates 35, thereby providing a narrow continuous zone through the rubber body 20 marked upper compression zone in the diagram. This zone is of uniform thickness across the mouth of the gap and is the only portion of the rubber body subjected to direct compression by the compressive force incident to a reduction in the width of the gap. In the diagram, compressive force on the particular portion of the rubber body 20 there shown is represented by the vectors P and P the line of action of these vectors being through the medial horizontal plane of the upper compression zone. It is evident that these compressive forces have little lateral displacing effect on the plates 35 since they act above the plates, and substantially all of the compressive force exerted on the upper compression zone is utilized in bulging the ridges 32 between the plates.

Inasmuch as the ridges on the bottom of the rubber body project downwardly between the plates to a crest 33, and there is a groove 26 opposite the crest 33 on the upper surface of the rubber body, it is evident that the centroid or mass-center Y of the rubber portion between adjacent plates, lies at a lower elevation than the line of action of the force vectors P and P Accordingly the compressive force represented by these vectors P and P acts to bulge the ridge downwardly and between the plates to the condition shown in FIG. 3.

The layer of rubber of the body portion 20 above the upper compression zone and between adjoining grooves 26 is not subjected to any substantial compression until the grooves 26 are fully closed. This advantageously prevents or minimizes bulging of the road surface of the rubber body. Moreover, because the opposite sides of the grooves 26 are convexly rounded, the grooves 26 progressively close from their bottoms outward. Thus, loose dirt or the like which may collect in the grooves is expelled upward from the grooves as they are progressively closed.

The term pleat portion as used herein and in the claims refers to the portions of the rubber body 20 indicated by this legend in FIG. 5 between any two adjoining plates which undergoes downward distortion when the joint is laterally compressed, and includes the portions of the rubber body 20 bounding the grooves 26. It is to be understood, however, that the invention is not limited to the particular shape of the pleat portions in the illustrated embodiment of the invention, and various shapes may be provided for the portion of the rubber between the plates to cause these portions to bulge downwardly when the joint is compressed.

As the pleat portions are compressed and bulged into the regions between the plates 35, there is apparently a reaction force exerted on the plates by the pleat portions 20 tending to jack or elevate the plates vertically toward the mouth of the gap. This jacking of the plates is counteracted in the preferred design shown by the shape of the spacers 40 as explained in the following remarks.

As shown in FIG. 15, the portions of the spacers 40 which are bonded or cemented to the plates are laterally aligned with each other from one plate to another between the end plates 35a and 35b. These portions of the spacers 40 form a lower compression zone designated on the diagram which is subjected to lateral compression by compressive forces incident to a reduction in width of the gap. These compressive forces are rep resented in the diagram by the vectors P and P and since the spacers 40 are medially crowned as at numeral 41, the line of action of forces P and P is at a lower elevation than the location of the centroid or mass center Z of the cross section of the spacers. Accordingly the force vectors P and P act not only to laterally compress the spacers 40 and to slide the plates 35 edgewise along sleeper slab 17, but also they act to bulge the spacers upwardly between the plates toward the rubber body 20. This bulging in turn tends to impose a downward thrust on plates 35 to keep their edges firmly seated on sleeper slab 17. Since the lower compression zone in FIG. 5 contains a volume of rubber much greater than the volume of rubber subjected to compression in the upper compression zone, the downward thrust on the plates produced by compression of the spacers 4t) greatly exceeds the upward or jacking effect which results by the distortion of the pleat portions. Consequently, in this design the plates 35 are urged progressively tighter against the sleeper slab 17 as the joint is progressively compressed.

The downward thrust exerted on the plates 35 by the spacers 40 may be further augmented by using a rubber compound for the spacers of higher durometer (which is therefore stiffer) than that for the rubber body 20. Preferably, the rubber body 20 may be about 45-60 shore A durometer, and the spacers 40 may be about 60-80 shore A durometer, in hardness.

When the concrete slabs contract to widen the expansion gap, the spacers 40 expand to separate the vertical plates and the pleat portions of the rubber body 20 likewise expand widthwise as the lateral compressive force is relieved. Since the end plates 35a and 35b are positively secured to the end faces 13 and 14 by the dowels 46, the joint will expand laterally with the end plates seated snugly against these walls.

The terms rubber or rubber-like as used herein and in the claims include both tree-grown substances and various man-made materials having the characteristic elasticity and extensibility of natural rubber. Preferably the rubber body 20 and the spacers 40 are made of a synthetic oil-resistant, sunlight-resistant vulcanizable compound such as neoprene, or the like. The body 20 is preferably compounded for durability about equivalent to that of conventional tire treads.

Variations in the construction disclosed may be made within the scope of the invention as it is defined in the appended claims.

We claim:

1. A highway expansion joint assembly comprising a pair of opposing concrete highway slabs having end surfaces spaced to provide opposing sides of an expansion gap, a structural member underlying the ends of said slabs to form the bottom of said gap, a body of flexible resilient rubber-like material covering the mouth of said gap, said body having lengthwise margins extending lengthwise of the opposing sides of the gap, means for fastening said margins to said opposing slabs in sealing engagement, said body further including a substantially smooth outer surface substantially flush with the roadway surfaces of said slabs and having on said outer surface a series of narrow shallow laterally spaced lengthwise-extending grooves, and said body having an opposite inner side having a series of lengthwise ridges, the crests of said ridges being disposed opposite corresponding grooves of said outer surface, a series of laterally-spaced rigid plates extending lengthwise of the gap intermediate the margins of said body, said plates having lower longitudinal edges bearing on the bottom of said gap and upper longitudial edges connected to and supporting said inner surface of the body in the valleys of said ridges, said ridges being adapted to distort downwardly between the plates in response to expansion of said slabs, a series of resilient rubber-like spacers between successive plates adjacent the lower longitudinal edges thereof, and means for transmitting compressive force from the sides of the gap to the outermost plates separated by said spacers, said spacers each having upper surfaces projecting closer toward said rubber body than the portions of said spacer engaging said plates and each said spacer being resiliently stiffer and therefore more resistant to compression than the portions of said rubber body adapted for distortion between the plates in response to movement of said slabs efiecting a reduction in the width of said gap.

2. In an expansion gap having opposing sides and a bottom portion defined by adjoining structural members, an expansion joint comprising a body of resilient flexible elastomeric material bridging said sides at the mouth of said gap, said body having a substantially plane upper surface in which there is a series of grooves extending lengthwise of the body, and said body having a lower surface on which there is a series of lengthwise ridges substantially opposite corresponding grooves of said outer surface, means connecting the margins of the body to said gap sides, a series of parallel rigid body-support members connectedly engaged with said lower surface between said ridges, said members being disposed alternately with said ridges and substantially perpendicular to said upper surface and being laterally slidable on the bottom of the gap in parallelism in response to changes in the Width of the gap and resilient spacer means independent of the body interconnecting adjoining members one to an other and with the sides of the gap and located between said body and the bottom of said gap.

3. In an expansion gap having opposing sides and a bottom portion defined by adjoining structural members, an expansion joint therein comprising a body of resilient flexible elastomeric material bridging said sides at the mouth of said gap, said body having a substantially plane upper surface and including two pleat portions extending lengthwise of the gap intermediate said sides, and a rigid body-supporting member extending lengthwise of the gap between the bottom of said gap and the opposing lower surface of the body at a region thereof between said pleat portions and being connected to said lower surface of the body, said pleat portions each comprising a ridge on the lower surface of said body extending lengthwise of the body and said gap, and a shallow groove in the upper surface of said body opposite said ridge whereby said pleat portion is adapted for distortion into and out of the regions of the gap on opposite sides of said rigid member without appreciably distorting said plane upper surface in response to changes in the width of said gap, and means to oppose displacement of said rigid member toward said body in response to a reduction in the width of said gap.

4. A road expansion joint assembly comprising two road members having end surfaces spaced to provide opposing sides of an expansion gap, a structural member underlying the ends of said road members to form the bottom of said gap, a body of flexible resilient elastomeric material covering the mouth of said gap, said body having lengthwise margins extending lengthwise of the opposing sides of the gap, means for fastening said margins to said opposing sides of the gap, said body further including a substantially smooth outer surface substantially flush with the roadway surfaces of said road members and having on said outer surface a series of narrow shallow laterally spaced lengthwise-extending grooves, and said body having an opposite inner side having a series of lengthwise ridges, the crests of said ridges being disposed opposite corresponding grooves of said outer surface, a series of laterally-spaced rigid plates extending lengthwise of the gap, said plates having lower longitudinal edges bearing on said member forming the bottom of said gap and upper longitudinal edges supporting and connected to said inner surface of the body in the valleys of said ridges, said ridges being adapted to distort downwardly between the plates in response to movement of said road members narrowing said gap, a series of resilient spacers between successive plates near the lower longitudinal edges thereof adapted for distortion between the plates in response to movement of said road members narrowing said gap and means for transmitting compressive force from the sides of the gap to the outermost plates separated by said spacers.

5. An expansion joint assembly comprising two members having ends laterally spaced to provide opposing sides of an expansion gap, a third member forming a bottom for said gap, a body of flexible resilient elastomeric composition covering the mouth of said gap, means for connecting lengthwise margins of said body to the sides of said expansion gap, said body having a substantially plane upper surface substantially flush with the adjoining surfaces of said gap members, rigid bodysupporting members extending lengthwise of said body intermediate the lengthwise margins thereof, said support members being supported on said bottom of said gap and connectedly engaged with the lower surface of said body portion to support said body portion against sagging between its lengthwise margins and the support members being in spaced relation one from another, resilient spacer means between adjoining support members at locations on the members intermediate said body and said bottom, means for transmitting compressive force from the sides of the gap to the outermost support members separated by said spacer means, the spacer means being adapted to resiliently oppose lateral movement of adjoining support members toward each other on said bottom in response to widthwise compression of said body as the gap becomes narrower, and the body including lengthwise portions between the locations on the body engaged by said support members which lengthwise portions are shaped for distortion into the region between adjoining support members to maintain said upper surface of said body substantially plane during said widthwise compression of said body.

6. An expansion joint comprising a body of flexible resilient elastomeric composition which body is generally thin compared with its length and width, said body having a substantially plane upper surface in which there is a series of grooves extending lengthwise of the body, and said body having a lower surface on which there is a series of lengthwise ridges substantially opposite corresponding grooves of said outer surface, a series of parallel rigid body-support members connected to said lower surface between said ridges, said members being disposed alternately with said ridges and substantially perpendicular to said upper surface, and means for retaining all said rigid members in supporting relation with said body and against displacement toward said body in response to lateral compressive forces on the sides of said body, said retaining means including resilient spacer elements separating adjoining rigid members one from another and outer spacer elements on the outwardly directed faces of the outermost rigid members, all said spacer elements being disposed at locations between said body and the extremities of said rigid members remote from said body, and said outermost spacer elements being adapted to transmit lateral compressive force to the outermost rigid members from the adjoining sides of an expansion gap in which said joint is installed.

7. An expansion joint according to claim 6 in which each said groove has a narrow bottom and diverging curved sides which blend smoothly into the upper surface of the body.

8. An expansion joint comprising a body of flexible resilient elastomeric composition having a substantially plane upper surface and the body being adapted for bridging an expansion gap between adjoining structural members with said upper surface substantially flush with adjacent surfaces of said structural members, at least one rigid body-supporting member extending lengthwise of said body intermediate the lengthwise margins of'said body, said support member being connected to the lower surface of said body portion to support said body portion against sagging between its lengthwise margins, and the body including lengthwise body portions flanking the location on the body engaged by said support member which lengthwise body portions are shaped for distortion into the region beside said support member to maintain said upper surface of said body substantially plane in response to widthwise compression of said body, and means for retaining said rigid member in supporting relation with said body and against displacement toward said body in response to lateral compressive forces on the sides of said body, said retaining means including resilient spacer elements on opposing sides of said support member at a location between said body and the 2,156,681 Dewhirst et a1 May 2, 1939 extremity of said support member remote from said body, 2,220,628 Stedman Nov. 5, 1940 said spacer elements being adapted to transmit lateral 2,225,496 Getkin et a1 Dec. 17, 1940 compressive force to said support member from th ad- 2,848,928 Gibson Aug. 26, 1958 ommg structural members in WhlCh sald oint 1s installed. 5 FOREIGN PATENTS References Cited in the file of this patent 17,164 Great Britain 1914 229,551 Great Britain Feb. 26, 1925 UNITED STATES PATENTS 835,240 France Sept. 19, 1938 2,111,114 Fischer Mar. 15, 1938 933,157 Germany Sept. 22, 1955 

